It's very useful to be able to comment out a block of code in a quick edit. And likewise to uncomment the code. This operation often involves multi-line stanzas and even large blocks. With just line-wise navigation and insert mode this would cost you about 4 keystrokes per line. Master this hole of VimGolf and you'll quickly drop your key count in day to day Vim as well.

Simple things we do all the time should be able to be done with very few keystrokes, but sometimes I find something I need to do makes me go, "There MUST be a better way."
This challenge is just a simple movement and entering text at a certain place.